This invention relates to handling apparatus and, more particularly, to method and apparatus for the insertion and removal of a section of belting in and from an extensible endless belt conveyor.
In long wall coal mining operations two parallel panels or gate entries are driven into the coal seam up to 1000 feet apart. The gate entries are joined by an entry at right angles which forms the long wall face. Successive strips are taken off the side of the face entry and the coal is deposited on a face conveyor which delivers it to a panel conveyor. As the strip is removed from the face, the conveyor is shortened to follow the removal equipment. As the conveyor is shortened, the endless belt is accumulated by a pulley system in the conveyor. To minimize the complexity of belt storage in the conveyor, it is common practice to remove a section of the belt and wind the removed section on a spool so that the belt may be stored and reinserted into the conveyor for a successive mining operation at another seam face.
The conventional manner in which belting sections are removed from the conveyor frame generally involve positioning a spool adjacent the head pulley of the conveyor. The storage reel may be part of a self propelled vehicle. The conveying reach is connected at a belt lacing splice and the section to be removed is wound from the conveyor by the spool which is powered by a hydraulic motor. The belt pull or tension developed and the winding speed are a function of the increasing diameter of the belt roll as the belt is wound on the spool. When the spool is empty, the belt pull or tension is at a maximum while the belt speed is at a minimum. As the diameter of the spool increases, the belt speed increases while the belt pull decreases. Since the belt section being removed from the conveyor is laced through a number of support rolls, a significant amount of pull on the belt is required to wind the belt on the spool. While tensile forces in the belt remain substantially constant during this winding operation, the torque loads on the winding motor are increased as a function of the radius of the material wound on the spool since the progressively increasing extent of the radius constitutes a moment arm with respect to the center of the winding shaft. The torque capacity of the winding motor in prior art devices is a function of the diameter of the wound belting rather than the torque required to merely overcome the resistance to the removal of the belt from the accumulator portion of the conveyor.
Examples of such prior art may be found in U.S. Pat. No. 2,846,051 to Craigs et al. and in U.S. Pat. No. 2,933,177, to Long.